You may have heard the phrase “the calf muscles are the second heart.”
While this is not a literal medical description, there is an important physiological reason behind the expression.
Your heart pumps blood through your arteries to deliver oxygen and nutrients throughout your body. But after blood reaches your legs and feet, it has to travel upward against gravity through the veins to return to the heart.
This is where the calf muscle pump becomes important.
When you walk, flex your ankles, rise onto your toes or contract your calf muscles, the muscles surrounding the deep veins of your lower leg contract and help push venous blood upward toward the heart.
Research describes the calf muscle pump as a major force contributing to venous blood return from the lower extremities.
This is why the calf is sometimes described as a “second heart” or “peripheral heart.”
It does not pump blood like the actual heart. Instead, it acts more like a muscular assistance system for venous circulation in the legs.
What Is the Calf Muscle Pump?
The calf muscle pump is the mechanism by which contractions of the calf muscles help move venous blood from the lower legs back toward the heart. Your lower legs contain a network of veins that carry blood back toward the heart.
When you are walking:
Calf contracts → veins are compressed → blood is pushed upward → valves help limit backward flow → calf relaxes → veins refill
This process happens repeatedly as you move.
The calf pump is particularly relevant because the lower limbs are below the heart, meaning gravity makes venous return more challenging than blood flow through many other parts of the body.
A research review describes the calf muscle pump as a key contributor to venous return from the lower extremities and notes its relationship .
Why Does the Calf Muscle Pump Matter?
It Helps Move Blood Back Toward the Heart
Arteries carry blood away from the heart under pressure generated largely by the heart's pumping action.
Veins operate differently.
Venous blood returning from the legs has to travel upward against gravity.
The calf muscle pump helps provide mechanical assistance during movement.
Every time your calf muscles contract, they can help compress veins in the lower leg and encourage blood to move upward.
This makes ordinary movement—such as walking—more than just exercise. Walking also repeatedly activates the calf muscle pump.
Sitting for Long Periods Reduces Calf Pump Activity
Think about what happens when you sit at a desk for several hours.
Your legs may barely move.
Your ankle joints remain relatively still.
Your calf muscles are therefore contracting much less frequently than they would while walking.
This does not mean that sitting automatically causes a circulation problem in every person.
However, prolonged immobility is associated with venous stasis and can contribute to blood-clot risk in certain situations, particularly during long-distance travel.
The CDC recommends moving the legs frequently during long trips and specifically suggests exercising the calf muscles while seated.
Simple movements include:
- raising and lowering your heels
- raising and lowering your toes
- flexing and extending your ankles
- tightening and releasing the leg muscles
- standing up and walking when possible
These movements periodically activate the muscles and joints of the lower leg.
Walking Naturally Activates the Calf Pump
One of the simplest ways to activate your calf muscles is also one of the most accessible:
Walk.
Every step involves coordinated movement through the foot, ankle and calf.
Walking therefore provides repeated contractions of the calf muscles throughout the day.
The World Health Organization recommends regular physical activity for adults and older adults, including aerobic activity and muscle-strengthening activities.
For adults, WHO recommends at least 150 minutes of moderate-intensity aerobic activity per week, or the equivalent amount of more vigorous activity.
You do not need to turn every walk into a workout.
Short periods of movement throughout the day can help reduce prolonged inactivity.
What Happens When You Activate Your Calf Muscles?
When the calf muscles contract, they can compress the veins running through the lower leg.
This helps create a pressure gradient that encourages venous blood to move upward.
The veins also contain valves that help limit backward movement of blood. The basic sequence can be simplified as:
This is the calf muscle pump in action.
The underlying physiology is more complex than this simplified illustration, but the basic concept explains why movement of the ankle and calf is relevant to venous circulation.
Is the Calf Muscle Really a “Second Heart”?
Not literally.
The phrase “second heart” is a useful metaphor, not an anatomical classification.
Your calf muscles do not generate the same kind of pressure or perform the same function as the heart.
The heart is the central muscular pump responsible for circulating blood through the cardiovascular system.
The calf muscle pump is a peripheral mechanism that assists venous return from the lower limbs.
So a more scientifically accurate way to say it is:
The calf muscles act as an important peripheral pump that assists the return of venous blood from the legs to the heart.
This distinction is particularly important when discussing circulation online because the “second heart” phrase can otherwise sound like the calf has the same function as the heart.
What happens when you sit for too long?
When you remain seated for a long time, your calf muscles are relatively inactive.
The lack of movement means there are fewer muscle contractions assisting venous return.
During long-distance travel, prolonged sitting can increase the risk of venous thromboembolism in some people. The CDC recommends regular movement, walking when possible and calf exercises during long trips.
This is particularly relevant for people who spend long hours:
- working at a desk
- travelling by plane
- travelling by car
- sitting through long meetings
- watching television
- recovering from periods of reduced mobility
A practical rule is simple:
If you have been sitting for a long time, look for a safe opportunity to move.
A Simple "Calf Pump" Routine For Your Day
You can incorporate calf activation into your daily routine without needing a gym.
Morning
10 – 20 heel raises
Use a wall or sturdy surface to balance if needed.
During work
10 – 20 seated heel raises + ankle pumps
Stand and walk around when practical
During travel
Raise & lower your heel and move your ankles regularly.
When possible, stand up and walk around.
The CDC recommends walking periodically during long-distance travel and exercising the calf muscles while seated.
Evening
Take a comfortablewalkor perform another form of physical activity appropriate for your fitness level.
The objective is not to force circulation.
The objective is to reduce prolonged inactivity and keep your lower legs moving.
How Often Should You Activate Your Calf Muscles?
There is no single scientifically established number of calf contractions that everyone needs each day.
Instead, think about regular movement.
For general health, WHO recommends that adults accumulate at least 150 minutes of moderate-intensity aerobic activity per week, alongside muscle-strengthening activities on at least two days per week.
Older adults should also incorporate balance-focused activity where appropriate.
For people who sit for extended periods, adding brief movement breaks can be a practical strategy. For example:
Sit → Move → Sit → Move → Walk → Move
rather than remaining stationary for many uninterrupted hours.
Who Should Be Careful With Calf Exercises?
For most healthy people, gentle calf movements and ordinary walking are generally part of normal physical activity. However, exercise should be adapted to individual circumstances. Speak with a healthcare professional before starting or significantly changing an exercise routine if you have:
- significant leg pain
- a recent leg injury or surgery
- severe swelling
- known vascular disease
- significant mobility limitations
- a history of blood clots
- a diagnosed heart or circulation condition
- another medical condition that affects exercise safety
Important: Know the Warning Signs of a Blood Clot
Do not try to treat suspected DVT simply by exercising the calf.
Seek prompt medical evaluation if you develop symptoms such as new or unexplained swelling, pain or tenderness in one leg, warmth or skin discoloration, particularly if symptoms develop suddenly.
If symptoms such as difficulty breathing, chest pain, coughing up blood or fainting occur, seek emergency medical attention.
The CDC notes that DVT can be serious and that pulmonary embolism can be life-threatening.
Calf Muscles & Healthy Ageing
The calf muscle pump becomes particularly interesting when we think about healthy ageing.
Maintaining lower-body strength and mobility can help support independence and everyday function.
Simple activities such as walking, rising onto your toes, climbing stairs and balance exercises can engage the muscles of the lower body.
WHO recommends that adults aged 65 and above include muscle-strengthening activities on at least two days per week and, for those with poor mobility, activities that enhance balance and help prevent falls on three or more days per week.
The goal is not necessarily to build large calf muscles.
It is to maintain the ability to move, walk, balance and perform everyday activities safely.
5 Easy Ways to Activate Your "Second Heart"
If you want to remember only five things, start here:
- Walk – Walking naturally contracts the calf muscles.
- Do heel raises – Stand safely and repeatedly raise and lower your heels.
- Move your ankles – Ankle pumps are easy to perform while seated.
- Break up long periods of sitting – Stand, stretch or walk when practical.
- Strengthen your legs regularly – Include lower-body strengthening as part of a balanced exercise routine.
Small movements performed regularly can add up.
References
Lattimer, C. R., Kalodiki, E., Azzam, M., & Geroulakos, G. (2013). Calf pump activity influencing venous hemodynamics in the lower extremity. International Angiology.
Davies, A. H. (2016). The calf muscle pump revisited. Journal of Vascular Surgery: Venous and Lymphatic Disorders.
Centers for Disease Control and Prevention (CDC). Blood Clots During Travel. Travelers' Health.
Centers for Disease Control and Prevention (CDC). (2024). Understanding Your Risk for Blood Clots with Travel. Venous Thromboembolism.
World Health Organization (WHO). Physical Activity. WHO Physical Activity Guidelines.
World Health Organization (WHO). (2020). WHO Guidelines on Physical Activity and Sedentary Behaviour.
World Health Organization (WHO). Everyday Actions for Better Health – WHO Recommendations.
Piazza, G. (2015). Cardiology Patient Page: Venous Thromboembolism. Circulation.